This invention relates in general to a memory device and more particularly to a two-dimensional analog memory monolithically integrated with insulated-gate field-effect transistors operating on the charge-transfer principle. A system with the aid of which a small picture of a selected second program can be made visible within the picture of a selected first program displayed on the screen of a television receiver has become known from the German Offenlegungsschrift (DE-OS) 26 28 737 corresponding to U.S. Pat. No. 4,139,860 as well as from an article published on pages 758 to 762 of the technical journal "Funkschau," 1977. For this purpose there are used in particular some additional highly integrated circuits of which one type serves to temporarily store the picture of the selected second program, and of which another type serves the time control of this display. In the course of this, the brightness signal of the picture of the second program, i.e. of the so-called small picture, in an alternating half picturewise manner is stored in the two partial memories of the analog memory, and read out. The storing is carried out in phase with the received small picture transmitter, whereas the readout is performed at about four times the speed thereof, at that particular time in which the small picture is displayed.
Practice has shown that the variations of the electrical properties of the two partial memories, owing to them being manufactured as separate integrated circuits, lead to visible interference effects in the displayed small picture, because the two half pictures as displayed, each have to pass through electrically different partial memories.